Programming Forums > Application Development > C++

strikefred0m · Oct 10th, 2008, 1:43 AM

Hi there, I am new there, and I searched before about my question, unfortunately I am unable to understand them and I post again. Sorry if repeating the same question.

My question is like this, ask the user to key in Max and Min as the random number range, and the random number should be in the range. All work fine but I am unable to prevent some percentage that the random generator will generate the same number. (I set the range between Max and Min must be at least same or greater than 10).

Max = top.
Min = low.
top - low >= 10.

The random generator will then generate 6 numbers in an array.

 c++ Syntax (Toggle Plain Text) 
for (index = 0; index < 6; index++)
{
	pcvalues[index] = (rand() + time (0)) % top ;
	if (pcvalues[index] < low)
	{
		do
		{
			pcvalues[index] = (pcvalues[index] + low ) % top;
		} while (pcvalues[index] < low);
	}
 
}
for (index = 0; index < 6; index++)
{
	pcvalues[index] = (rand() + time (0)) % top ;
	if (pcvalues[index] < low)
	{
		do
		{
			pcvalues[index] = (pcvalues[index] + low ) % top;
		} while (pcvalues[index] < low);
	}
	
}

Can anyone tell me how to prevent same number repetition?

Thank a lot.

Sane · Oct 10th, 2008, 2:13 AM

This thread has appeared many times in this forum. One example is linked to at the bottom of this page under "similar threads". http://www.programmingforums.org/thread12570.html

Here is another example that was just posted last week: http://www.programmingforums.org/showthread.php?t=16612

You said you searched but "don't understand them"? What don't you understand about the code? Or is your question something slightly different?

strikefred0m · Oct 10th, 2008, 3:15 AM

http://www.programmingforums.org/showthread.php?t=16612

The thread was afterward goes into Java thing isn't? I am just newbie to C++ and currently only been tough until array...

http://www.programmingforums.org/thread12570.html

for(i=0;i<100;++i)
a[i] = i+1;

for(i=0;i<100;++i)
swap(a[i], a[rand()%100]);

Sorry I can't link it to my question, can you please give an short explanation? Thank for your kind help.

devoox · Oct 15th, 2008, 5:52 AM

Well, if you read the whole threads, but not just checking the question, you would have found the "link" to your question - srand() function

RareDevil · Oct 16th, 2008, 11:26 AM

If you want to have fun with random numbers then try to look at this code. It was one of the first i have made.

 c++ Syntax (Toggle Plain Text) 
#include <iostream>
#include <cstdlib>
#include <ctime>
#include <fstream>
 
using namespace std;
 
int outPut();
int inPut();
int textOut();
 
int main()
{
  srand( (unsigned) time(0) );
  int tempRand;
  int even = 0;
  int temp;
  long int sample = 1000000000;
  ofstream my_stream("outFile.txt", ios::trunc);
  ifstream in_stream;
  for (int i = 0; i < sample; i++)
  {
    tempRand = (rand()%9999) + 1;
    my_stream << tempRand << endl;
  }
  my_stream.close();
  in_stream.open("outFile.txt");
  while ( in_stream )
  {
    in_stream >> temp;
    if ( (temp % 2) == 0 )
       even++;
  }
  cout << "Total Numbers = " << sample << endl
       << "Even: " << even << endl
       << "Odd: " << sample - even << endl;
  system("pause");
  return 0;
}
#include <iostream>
#include <cstdlib>
#include <ctime>
#include <fstream>

using namespace std;

int outPut();
int inPut();
int textOut();

int main()
{
  srand( (unsigned) time(0) );
  int tempRand;
  int even = 0;
  int temp;
  long int sample = 1000000000;
  ofstream my_stream("outFile.txt", ios::trunc);
  ifstream in_stream;
  for (int i = 0; i < sample; i++)
  {
    tempRand = (rand()%9999) + 1;
    my_stream << tempRand << endl;
  }
  my_stream.close();
  in_stream.open("outFile.txt");
  while ( in_stream )
  {
    in_stream >> temp;
    if ( (temp % 2) == 0 )
       even++;
  }
  cout << "Total Numbers = " << sample << endl
       << "Even: " << even << endl
       << "Odd: " << sample - even << endl;
  system("pause");
  return 0;
}

You maybe need to change "long int sample = 1000000000;" to somethign like "long int sample = 1000000;" or a less number else will this little program make a 5GB txt file

Oct 10th, 2008, 1:43 AM	#1
strikefred0m Newbie Join Date: Oct 2008 Posts: 2 Rep Power: 0	Repeated Random Number Hi there, I am new there, and I searched before about my question, unfortunately I am unable to understand them and I post again. Sorry if repeating the same question. My question is like this, ask the user to key in Max and Min as the random number range, and the random number should be in the range. All work fine but I am unable to prevent some percentage that the random generator will generate the same number. (I set the range between Max and Min must be at least same or greater than 10). Max = top. Min = low. top - low >= 10. The random generator will then generate 6 numbers in an array. c++ Syntax (Toggle Plain Text) for (index = 0; index < 6; index++) { pcvalues[index] = (rand() + time (0)) % top ; if (pcvalues[index] < low) { do { pcvalues[index] = (pcvalues[index] + low ) % top; } while (pcvalues[index] < low); } } for (index = 0; index < 6; index++) { pcvalues[index] = (rand() + time (0)) % top ; if (pcvalues[index] < low) { do { pcvalues[index] = (pcvalues[index] + low ) % top; } while (pcvalues[index] < low); } } Can anyone tell me how to prevent same number repetition? Thank a lot. Last edited by big_k105; Oct 16th, 2008 at 12:21 PM. Reason: Changed quote tag to code tag

Oct 10th, 2008, 2:13 AM	#2
Sane Banned Join Date: Apr 2005 Location: Waterloo, Ontario Posts: 2,101 Rep Power: 6	Re: Repeated Random Number This thread has appeared many times in this forum. One example is linked to at the bottom of this page under "similar threads". http://www.programmingforums.org/thread12570.html Here is another example that was just posted last week: http://www.programmingforums.org/showthread.php?t=16612 You said you searched but "don't understand them"? What don't you understand about the code? Or is your question something slightly different? __________________ Looking for tough programming challenges? Try participating in Sane's Monthly Algorithms Challenges! Composing Techno is a little side hobby of mine. Techno by DJ Sane. All free for download.

Oct 10th, 2008, 3:15 AM	#3
strikefred0m Newbie Join Date: Oct 2008 Posts: 2 Rep Power: 0	Re: Repeated Random Number http://www.programmingforums.org/showthread.php?t=16612 The thread was afterward goes into Java thing isn't? I am just newbie to C++ and currently only been tough until array... http://www.programmingforums.org/thread12570.html for(i=0;i<100;++i) a[i] = i+1; for(i=0;i<100;++i) swap(a[i], a[rand()%100]); Sorry I can't link it to my question, can you please give an short explanation? Thank for your kind help.

Oct 15th, 2008, 5:52 AM	#4
devoox Newbie Join Date: Sep 2008 Posts: 3 Rep Power: 0	Re: Repeated Random Number Well, if you read the whole threads, but not just checking the question, you would have found the "link" to your question - srand() function

Oct 16th, 2008, 11:26 AM	#5
RareDevil <html>#include C++<?php?> Join Date: Oct 2008 Location: Denmark Posts: 14 Rep Power: 0	Re: Repeated Random Number If you want to have fun with random numbers then try to look at this code. It was one of the first i have made. c++ Syntax (Toggle Plain Text) #include <iostream> #include <cstdlib> #include <ctime> #include <fstream> using namespace std; int outPut(); int inPut(); int textOut(); int main() { srand( (unsigned) time(0) ); int tempRand; int even = 0; int temp; long int sample = 1000000000; ofstream my_stream("outFile.txt", ios::trunc); ifstream in_stream; for (int i = 0; i < sample; i++) { tempRand = (rand()%9999) + 1; my_stream << tempRand << endl; } my_stream.close(); in_stream.open("outFile.txt"); while ( in_stream ) { in_stream >> temp; if ( (temp % 2) == 0 ) even++; } cout << "Total Numbers = " << sample << endl << "Even: " << even << endl << "Odd: " << sample - even << endl; system("pause"); return 0; } #include <iostream> #include <cstdlib> #include <ctime> #include <fstream> using namespace std; int outPut(); int inPut(); int textOut(); int main() { srand( (unsigned) time(0) ); int tempRand; int even = 0; int temp; long int sample = 1000000000; ofstream my_stream("outFile.txt", ios::trunc); ifstream in_stream; for (int i = 0; i < sample; i++) { tempRand = (rand()%9999) + 1; my_stream << tempRand << endl; } my_stream.close(); in_stream.open("outFile.txt"); while ( in_stream ) { in_stream >> temp; if ( (temp % 2) == 0 ) even++; } cout << "Total Numbers = " << sample << endl << "Even: " << even << endl << "Odd: " << sample - even << endl; system("pause"); return 0; } You maybe need to change "long int sample = 1000000000;" to somethign like "long int sample = 1000000;" or a less number else will this little program make a 5GB txt file

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
non-repetitive random number	malms	C	4	Feb 14th, 2007 1:17 PM
Random Number	coldDeath	Python	1	Sep 11th, 2005 9:17 AM
Random Number & Average Problem	Hadrurus	Java	6	Aug 15th, 2005 2:08 PM
generate a random number	cwl157	Java	3	Apr 15th, 2005 7:18 PM
non repeating random number generation	gencor45	C#	2	Feb 9th, 2005 1:11 AM

Programming Forums > Application Development > C++

Repeated Random Number